阅读理解。

     Secondhand smoke is a byproduct of cigarette, cigar or pipe smoking. Secondhand smoke occurs

when tobacco burns or when smokers exhale, and it is inhaled (吸入)involuntarily by non-smokers.

     Secondhand smoke___________________. The first is called side stream smoke, which is the

smoke released from the burning end of a cigarette or cigar, or from tobacco burning in the bowl of

a pipe. The second is called mainstream smoke, which is exhaled by a smoker.

     When nonsmokers are exposed to secondhand smoke, they inhale many of the same cancer-causing

chemicals that smokers inhale. According to the U.S. Surgeon General, cigarette smoke contains more

than 4,000 chemical compounds, including more than 50 cancer-causing chemicals, and at least 250

chemicals that are either toxic or carcinogenic.

     Both side stream and mainstream smoke are dangerous to nonsmokers. Side stream smoke is

generated at lower temperatures and under different conditions than mainstream smoke. As a result, it

contains higher concentrations of many of the toxins found in cigarette smoke.

     Secondhand smoke has been designated as a known human carcinogen by the U.S. Environmental

Protection Agency, the National Toxicology Program, and the International Agency for Research on

Cancer. Secondhand smoke also is listed as an occupational carcinogen by the National Institute for

Occupational Safety and Health.

     According to the 2006 report by the U.S. Surgeon General, there is no risk-free level of exposure

to secondhand smoke: even small amounts of secondhand smoke exposure can be harmful to people's

health. Separating smokers from nonsmokers, cleaning the air, and ventilating buildings can help.

However, they cannot eliminate the exposure of nonsmokers to secondhand smoke.

1.What is the main idea of the text? (no more than 10 words)

    _________________________________________________________ 

2. Which sentence in the text is closest in meaning to the following one?

In whatever way, people can’t get rid of the risk of nonsmokers to secondhand smoke

completely.

     _________________________________________________________

3. Fill in the blank in Paragraph 2 with proper words. (no more than 8 words)

     _________________________________________________________

4. Name at least three ways that will help reduce the harm of secondhand smoke.

  (no more than 12 words)

     _________________________________________________________

5. Translate the underlined sentence in Paragraph 3 into Chinese.

     _________________________________________________________